1. Field of the Invention
The present invention is related to electronic musical instruments which generate musical tones according to melody pattern information, and particularly, to electronic musical instruments in which the scale of a melody can be modified by specifying a chord progression and key.
2. Description of the Prior Art
Electronic musical instruments have conventionally been known wherein a user inputs a melody pattern such as a melody accompaniment from a panel or the like or selects a previously registered pattern, and supplies an arbitrary chord progression to the melody pattern, thereby to convert the scale according to a chord and generate musical tones. In such electronic musical instruments, conventionally, only one of the scales such as Ionian, Aeolian and the like has been made to correspond to chord types such as M (major) and m (minor).
FIG. 14 is a flowchart representing a typical operation of such conventional electronic musical instruments as described above. In step S30, a key and a chord progression is input. Each chord information of the chord progression is input along with its switching timing information and stored in a memory. It is assumed here that the input key is G and the chord progression is [Bm7- Em7-Am7-. . . ], for instance. In step S31, 1 is set in a chord counter i. In step S32, the chord type(x) vs. scale table of FIG. 15 is used to decide a scale according to the type of the input chord(x). In step S33, the melody pattern is modified so as to suit the scale decided in step S32 and musical tones are generated. In step S34, 1 is added to the counter i, and in step S35, it is examined whether or not the value of the counter i has exceeded the number of chords n; if not, the operation flow returns to step S32 to repeat decision of a scale corresponding to the next chord and modification of the scale of the melody pattern, thereby for playing the melody.
FIG. 12A is an example of the scales selected by the conventional method. Since the chord types of the input chord progression [Bm7-Em7-Am7-. . . ] are all m7, Aeolian is chosen for all according to the table of FIG. 15. Accordingly, the scales as shown in FIG. 12A are selected from the root of each chord. However, comparing these scales with a major scale which has G as tonic, there are mismatches in intervals as shown by arrows.
By nature, tones according with a scale sound musically natural, whereas those disaccording with a scale sound very unnatural. However, conventional method as described above had a problem that if an arbitrary chord progression was given to a melody pattern such as a accompaniment pattern to generate the musical tones of the melody pattern, scale-out tones corresponding to a specified key sometimes occurred.